Role of diquark correlations and the pion cloud in nucleon elastic form factors

Abstract

Electromagnetic form factors of the nucleon in the space-like region are investigated within the framework of a covariant and confining Nambu-Jona-Lasinio model. The bound state amplitude of the nucleon is obtained as the solution of a relativistic Faddeev equation, where diquark correlations appear naturally as a consequence of the strong coupling in the colour $\bar{3}$ $qq$ channel. Pion degrees of freedom are included as a perturbation to the "quark-core" contribution obtained using the Poincaré covariant Faddeev amplitude. While no model parameters are fit to form factor data, excellent agreement is obtained with the empirical nucleon form factors (including the magnetic moments and radii) where pion loop corrections play a critical role for $Q^2\lesssim 1$GeV${}^2$. Using charge symmetry, the nucleon form factors can be expressed as proton quark sector form factors. The latter are studied in detail, leading, for example, to the conclusion that the $d$-quark sector of the Dirac form factor is much softer than the $u$-quark sector, a consequence of the dominance of scalar diquark correlations in the proton wave function. On the other hand, for the proton quark sector Pauli form factors we find that the effect of the pion cloud and axialvector diquark correlations overcomes the effect of scalar diquark dominance, leading to a larger $d$-quark anomalous magnetic moment and a form factor in the $u$-quark sector that is slightly softer than in the $d$-quark sector.

arXiv comment30 pages and 40 figures

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• Charge Symmetry Breaking Effects in Pion and Kaon Structure
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• Quark spin and orbital angular momentum from proton GPDs
• Valence-quark distributions of pions and kaons in a nuclear medium
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• The magnetic moments and electromagnetic form factors of the decuplet baryons in chiral perturbation theory
• Impact of DCSB and dynamical diquark correlations on proton GPDs
• Nucleon Quark Distribution Functions from the Dyson-Schwinger Equations
• Generalized parton distributions in spin-3/2 particles
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• On the form factors of $d^{\ast }(2380)$
• Nuclear medium meson structures from the Schwinger proper-time Nambu--Jona-Lasinio model
• Study of the in-medium nucleon electromagnetic form factors using a light-front nucleon wave function combined with the quark-meson coupling model
• Baryons and the Borromeo
• Properties of neutral mesons in a hot and magnetized quark matter: size-dependent effects
• An Improved Hadronic Model for Pion Electroproduction
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• Quark-Meson Coupling model based upon the Nambu-Jona Lasinio model
• Intrinsic Glue and Wilson lines within Dressed Quarks
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• The kaon off-shell generalized parton distributions and transverse momentum dependent parton distributions
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• Flavour decomposition of electromagnetic transition form factors of nucleon resonances
• Chiral Corrections to Baryon Electromagnetic Form Factors